Software projects/OS/Slackware/Advanced usage/Hardening

About this document

• It's a WIP. Security is a huge subject. May take monthes to have something consistent here.
• I'm not a security expert.

GNU/Linux and free software

• Slackware, as almost every Linux distribution, is not secured by default. In fact, almost no Linux distribution is shipped with an acceptable security level.
• It's up to the administrator to work it out to the needed security level.
• When nicely secured, the main danger will come from the administrator's lack of attention.
• Avoid weakening your network with proprietary OS, even UNIX-based:

There's people who know things about the proprietary OS that you don't know.

• It means big proprietary vendors can put one hundred backdoors in their OS. When someone finds one, they will release a patch saying "Look at how we are trusty, we patched in less than one day". Still, there's ninety-nine backdoors left for them to sell.
• Use free software.

The physical access

• This is the most critical and dangerous vulnerability. When someone can get a physical access to your devices, you're potentially screwed.
• If you intend to hire or work with someone who calls himself a security expert, ask him what is the most dangerous vulnerability. If he doesn't answer this, throw him away, and far.

The installed programs

• The more programs installed, the more potential weaknesses.
• To install a minimal Slackware system, a good start is to take a look at tagfiles.
• They are located in the installation packages series. Tagfile example: the "a" (base system) serie tagfile: http://ftp.slackware.pl/pub/armedslack/armedslack-13.37/slackware/a/tagfile

The updates

• Of course, updates are critical.
• See this.

The kernel

• For a top-level security, you have to recompile your kernel as non-modular, only including the needed options.
• There's pros and cons about using a long-term stable or a latest kernel. I'm not able to give enlightened advices on this subject.

The devices

• Following my advice about the physical access, don't let anybody plug any device into your machines, especially USB ones.

The security tools

• chkrootkit
• rkhunter
• snort
• Nessus